Systems and methods for optical proximity detection with multiple field of views

ABSTRACT

An optical proximity detector includes a plurality photodetectors (PDs) and a winner-take-all (WTA) circuit. Each of the PDs has a respective field of view (FOV) and produces a respective analog current detection signal indicative of light incident on and detected by the PD. In an embodiment, the WTA circuit includes a comparator and a multiplexor (MUX). The comparator compares the analog current detection signals produced by the PDs and produces a selection signal in dependence thereon. The MUX receives the analog current detection signals produced by the PDs and outputs one of the analog current detection signals in dependence on the selection signal produced by the comparator. Circuitry, which is shared by the PDs, produces a digital detection signal corresponding to the one of the analog current detection signals output by the MUX. Such design can be used to reduce power consumption, size and cost of an optical proximity detector.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/010,947, filed Jun. 11, 2014, which is incorporated herein byreference.

BACKGROUND

Optical proximity detectors are often included in systems, such asconsumer products and/or other types of products, to detect the presenceof obstacles or other objects within one or more field-of-views (FOVs),so that the systems can respond to such detections. For example, anautonomous robot may use an optical proximity detector to detect when anobstacle is in its way, so that they robot may move around the obstacle.For another example, a vehicle may include an optical proximity detectorto notify a driver when the driver is driving to close to anothervehicle, or when an object is behind the vehicle when the vehicle isbacking up. For still another example, an optical proximity detector canbe used to help control a driverless vehicle. These are just a fewexamples, which are not meant to be all encompassing.

It is desirable to reduce the power consumed by optical proximitydetectors and to reduce the size and cost of optical proximitydetectors, especially when optical proximity detectors are used inmobile devices that are battery powered and/or relatively small in size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a high level block diagram of an exemplary optical proximitydetector.

FIG. 2 is a high level block diagram of an exemplary optical proximitydetector which includes a multiplexer that enables a single amplifierand analog-to-digital converter (ADC) to be shared by multiplephotodetectors (PDs).

FIG. 3 is a high level block diagram of an optical proximity detectoraccording to an embodiment of the present invention.

FIG. 4 illustrates an implementation of the comparator, introduced inFIG. 3, according to an embodiment of the present invention.

FIG. 5 is a high level flow diagram that is used to describe methodsaccording to various embodiments of the present invention.

FIG. 6 illustrates an exemplary system accordance to an embodiment ofthe present invention.

FIG. 7 illustrates an exemplary timing diagram for exemplary signalsthat can be used to control the light source(s), the comparator and theADC of an optical proximity sensor in accordance with an embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown byway of illustration specific illustrative embodiments. It is to beunderstood that other embodiments may be utilized and that mechanicaland electrical changes may be made. The following detailed descriptionis, therefore, not to be taken in a limiting sense. In the descriptionthat follows, like numerals or reference designators will be used torefer to like parts or elements throughout. In addition, the first digitof a reference number identifies the drawing in which the referencenumber first appears.

FIG. 1 shows an exemplary optical proximity detector 102, which can beused to detect the presence of an object, estimate proximity of anobject and/or detect motion of an object. The optical proximity detector102 includes an emitter portion including a light source 104, a driver106 and a timing controller 108. Additionally, the optical proximitydetector 102 includes a detector portion that is shown as including twooptical detection channels. A first optical detection channel includes aphotodetector (PD) 114 ₁, and a second optical detection channelincludes a PD 114 ₂. In this embodiment, the first optical detectionchannel also include a transimpedance amplifier (TIA) 116 ₁, aprogrammable gain amplifier (PGA) 118 ₁ and an analog-to-digitalconverter (ADC) 120 ₁. Similarly, the second optical detection channelalso includes a TIA 116 ₂, a PGA 118 ₂ and an ADC 120 ₂. While only twooptical detection channels are shown in FIG. 1, more than two opticaldetection channels are also possible. In other words, there can be nseparate optical detection channels, where n≧2. Each PD 114 ₁, 114 ₂ hasits own field of view (FOV), which may or may not overlap with the FOVof another PD. More generally, where there are n separate PDs, there aren separate FOVs, each of which may or may not overlap one or more otherFOVs, depending upon implementation (e.g., depending upon relativelocations and distances between PDs, the the FOV of each PD).

The PDs 114 ₁, 114 ₂ can be individually referred to as a PD 114, andcan collectively be referred to as the PDs 114. The TIAs 116 ₁, 116 ₂can be individually referred to as a TIA 116, and can collectively bereferred to as the TIAs 116. The PGAs 118 ₁, 118 ₂ can be individuallyreferred to as a PGA 118, and can collectively be referred to as thePGAs 118. Similarly, the ADCs 120 ₁, 120 ₂ can be individually referredto as an ADC 120, and can collectively be referred to as the ADCs 116.

The driver 106 is controlled by a transmit (TX) signal output by thetiming controller 108 or some other controller to selectively drive alight source 104. The driver 106 is generally shown as including acurrent source I₁ and a switch S₁ that is selectively closed based onthe transmit (TX) signal output by the timing controller 108. When theswitch S₁ is closed, the current produced by the current source I₁ isprovided to the anode of the light source 104, to thereby selectivelycause light to be emitted. Alternatively, the TX signal can selectivelycause a current to be pulled through the light source 104, e.g., bycoupling the switch S₁ and the current source I₁ between the cathode ofthe light source 104 and a low voltage rail (e.g., ground), to therebycause light to be emitted. In such an alternative configuration, thecurrent source may be referred to as a current sink.

The light source 104 can be, e.g., one or more light emitting diode(LED) or laser diode, but is not limited thereto. Depending uponimplementation and application, the different light detection channelscan have their own light source 104, or they may share the same lightsource 104. While infrared (IR) light sources are often employed inoptical proximity detectors, because the human eye cannot detect IRlight, the light source 104 can alternatively produce light of otherwavelengths. Each PD 114 can be, e.g., one or more photodiode, but isnot limited thereto. In embodiments including multiple light sources 104(e.g., one for each light detection channel), each light source caninclude its own driver 106 that is controlled by the transmit (TX)signal output by the timing controller 108.

Each PD 114 generates a current detection signal that is indicative ofthe intensity and phase of the light incident on and detected by the PD114. Each TIA 116 converts the current detection signal produce by thePD 114, to which the TIA is connected, to a voltage detection signal.Each PGA 118, or more generally amplifier, amplifies the voltagedetection signal output by the TIA 116 before it is provided to the ADC120. The ADC 120 digitizes the voltage detection signal, and moregenerally, produces a digital output signal (e.g., an N-bit signal) thatcan be used to detect the presence, proximity and/or motion of an objectwithin the FOV of the PD 114.

Optical proximity detectors, such as the one shown in FIG. 1, are oftenincluded in systems, such as consumer products and/or other types ofproducts, to detect the presence of obstacles or other objects withinone or more FOVs, so that the systems can response to such detections.For example, an autonomous robot may use an optical proximity detectorto detect when an obstacle is in its way, so that they robot may movearound the obstacle. For another example, a vehicle may include anoptical proximity detector to notify a driver when the driver is drivingtoo close to another vehicle, or when an object is behind the vehiclewhen the vehicle is backing up. For still another example, an opticalproximity detector can be used to help control a driverless vehicle.These are just a few examples, which are not meant to be allencompassing.

It is desirable to reduce the power consumed by optical proximitydetectors and to reduce the size and cost of optical proximitydetectors, especially when optical proximity detectors are used inmobile devices that are battery powered and/or relatively small in size.Embodiments of the present invention, which are described herein, can beused to achieve one or more of the aforementioned desirable features ofoptical proximity detectors.

FIG. 2 illustrates an exemplary optical proximity detector 202 whichincludes a multiplexer 222 that enables a single PGA 118 and a singleADC 120 to be shared by multiple PDs 114. However, if there is a desireto compare the intensity and/or phase of the light incident on the PD114 ₁ to the intensity and/or phase of the light incident on the PD 114₂, the optical proximity detector 202 has a few disadvantages. Forexample, a first digital output of the ADC 120 (producing during a firstperiod of time during which the MUX 222 outputs the signal it receivesfrom the TIA 116 ₁) needs to be saved in order for it to be compared toa second digital output of the ADC 120 (produced during a second periodof time during which the MUX 222 outputs the signal it receives from theTIA 116 ₂). In other words, analog-to-digital conversions need to beperformed sequentially, which slows down performance, and necessitatesthat one or more outputs of the ADC 120 be stored to allow forcomparisons of different outputs of the ADC 120. Additionally, theposition(s) of object(s) within the FOVs of the multiple PDs 114 maychange from the first period of time to the second period of time,potentially reducing the accuracy and usefulness of results of theaforementioned comparisons.

FIG. 3 illustrates an optical proximity detector 302, which can also bereferred to as an optical proximity sensor 302, according to anembodiment of the present invention. The light source 104, driver 106and timing controller 108 operate in the same manner as discussed abovewith reference to FIG. 1, and thus need not be described again. Asmentioned above, each of the different light detection channels can havetheir own light source 104, or they may share the same light source 104.The PD 114 ₁ generates a first current detection signal that isindicative of the intensity and phase of light emitted by the lightsource 104 that reflect off an object (within the FOV1) and is incidenton and detected by the PD 114 ₁. At the same time, the PD 114 ₂generates a second current detection signal that is indicative of theintensity and phase of light that reflect off an object (within theFOV2) and is incident on and detected by the PD 114 ₂. Where the lightsource 104 emits IR light, it is preferably that each of the opticaldetection channels is primarily responsive to detected IR light, andmore generally, that ambient light is rejected. To reject ambient light,an optical IR rejection filter can be placed over each PD 114. Otherknown as well as future developed techniques for rejecting ambient lightcan alternatively or additionally be used. Regardless of what ambientlight rejection technique is used, where the light source 104 emits IRlight the first current detection signal produced by the PD 114 ₁ ispreferably primarily indicative of the intensity and phase of IR lightemitted by the light source 104 that reflect off an object (within theFOV1) and is incident on and detected by the PD 114 ₁. Similarly, thesecond current detection signal produced by the PD 114 ₂ is preferablyprimarily indicative of the intensity and phase of IR light emitted bythe light source 104 (or another light source) that reflect off anobject (within the FOV2) and is incident on and detected by the PD 114₂.

A comparator 324 compares the first and second current signals, andbased on the comparison, selects which one of the first and secondcurrent signals is output by a multiplexer (MUX) 322. In other words,the comparator 324 produces a selection signal that is used to controlthe MUX 322. The output of the MUX 322 is provide to a TIA 116, whichconverts the current signal (output by the MUX 322) to a voltage signal.The PGA 118 amplifies the voltage signal output by the TIA 116, and theADC 120 converts the amplified voltage signal (output by the PGA 118) toa digital signal. In this embodiment, a single TIA 116, a single PGA 118and a single ADC 120 are shared by multiple PDs 114, without thedisadvantages discussed above with reference to FIG. 2. For example,analog-to-digital conversions need not be performed sequentially.Further, there is no need to store one or more outputs of the ADC 120 toallow for comparisons of different outputs of the ADC 120. The TIA 116,PGA 118 and ADC 120 are an example of circuitry that produces a digitaldetection signal corresponding to the one of the analog currentdetection signals output by the MUX. Such circuitry is advantageouslyshared by multiple optical channels. The use of alternative circuitrythat is shared by multiple channels is also possible and within thescope of an embodiment.

In accordance with an embodiment, the comparator 324 compares theamplitude of the first current signal (produced by the PD 114 ₁) to theamplitude of the second current signal (produced by the PD 114 ₂) toidentify which amplitude is greater, and controls the MUX 322 to causethe current signal having the greatest amplitude to be output by the MUX322. Accordingly, the comparator 324 and the MUX 322 can be collectivelyreferred to as a current amplitude winner-take-all (WTA) circuit 326. Anexemplary implementation of the comparator 324, which compares theamplitude of the first current signal (produced by the PD 114 ₁) to theamplitude of the second current signal (produced by the PD 114 ₂) toidentify which amplitude is greater, is shown in and described belowwith reference to FIG. 4. In this embodiment, if there is an objectwithin only one of the FOVs, then the current signal having the greatestamplitude corresponds to the PD having the object within its FOV. Ifthere is an object within more than one of the FOVs, then the currentsignal having the greatest amplitude corresponds to the PD having theclosest object within its FOV.

In accordance with another embodiment, the comparator 324 compares aphase associated with the first current signal (produced by the PD 114₁) to a phase associated with the second current signal (produced by thePD 114 ₂). For example, the phase associated with the first currentsignal (produced by the PD 114 ₁) can be the phase difference betweenthe first current signal and the TX signal (which can be provided to thecomparator, as indicated by the dashed line 328) or some other referencesignal. Similarly, the phase associated with the second current signal(produced by the PD 114 ₂) can be the phase difference between thesecond current signal and the TX signal or the other reference signal.In this embodiment, the comparator 324 compares the phase differenceassociated with the first current signal (produced by the PD 114 ₁) tothe phase difference associated with the second current signal (producedby the PD 114 ₂) to identify the smallest phase difference relative tothe TX signal or some other reference signal. In this embodiment, ifthere is an object within only one of the FOVs, then the current signalhaving the smallest phase difference corresponds to the PD having theobject within its FOV. If there is an object within more than one of theFOVs, then the current signal having the smallest phase differencecorresponds to the PD having the closest object within its FOV.Accordingly, in this embodiment the comparator 324 and the MUX 322 canbe collectively referred to as a phase difference winner-take-all (WTA)circuit 326.

An exemplary implementation of the comparator 324, which compares theamplitude of the first current signal (produced by the PD 114 ₁) to theamplitude of the second current signal (produced by the PD 114 ₂) toidentify which amplitude is greater, will now be described withreference to FIG. 4. Referring to FIG. 4, transistors M1-M4 and acurrent source I1 are configured as a first low impedance input circuit432 ₁. Transistors M11-M14 and a current source I2 are configured as asecond low impedance input circuit 432 ₁. Transistors M5-M8 and M15-M17are configured as a current amplitude comparator 434, with the inputs ofthe current amplitude comparator 434 being the gates of the transistorsM7 and M8. The current sources I1 and I2 are matched and are used tobias (and more specifically increase) the currents provided to inputs ofthe current amplitude comparator 434. Bias voltages vb1, vb2, vb3 andvb4 are used to bias various transistors. The switches S1 and S2, whichare opened and closed at the same time, are used to selectively providethe first and second current signals, produce respectively by the PD 114₁ and the PD 114 ₂, to the comparator 324 (and more specifically, to thelow impedance input circuits 432). The transistor M15 is turned on andoff in dependence which one of the first and second current signals isthe greater. When the first current signal (produced by the PD 114 ₁) isgreater than the second current signal (produced by the PD 114 ₂), thenthe transistor M15 is turned on, and the input to a latch 436 is high.When the second current signal (produced by the PD 114 ₂) is greaterthan the first current signal (produced by the PD 114 ₁), then thetransistor M15 is turned off, and the input to the latch 436 is low. Thelatch 436 latches either a low or high logic state, which is used tocontrol the MUX 322. In other words, the latch stores the select signal.When the first current signal (produced by the PD 114 ₁) is greater thanthe second current signal (produced by the PD 114 ₂), a high logic stateis latched by the latch 436, which causes the MUX 322 to output thefirst current signal (produced by the PD 114 ₁). When the second currentsignal (produced by the PD 114 ₂) is greater than the first currentsignal (produced by the PD 114 ₁), a low logic state is latched by thelatch 436, which causes the MUX 322 to output the second current signal(produced by the PD 114 ₂).

Advantages of the embodiments described with reference to FIG. 3 andFIG. 4 is that they require less analog circuitry than the embodimentsshown in FIGS. 1 and 2. Additionally, embodiments described withreference to FIG. 3 and FIG. 4 consume less power than embodiments shownin FIGS. 1 and 2. Further, embodiments described with reference to FIG.3 and FIG. 4 are faster than the embodiment shown in FIG. 2.

While only two optical detection channels are shown in FIG. 3, more thantwo optical detection channels are also possible. In other words, therecan be n separate optical detection channels, where n≧2, with eachchannel including its own PD 114. Each PD 114 has its own field of view(FOV), which may or may not overlap with the FOV of another PD. Wherethere are more than two PDs, and thus more the two FOVs, the comparator324 is configured to compare more than two signals to one another, andthe MUX 322 has more than two inputs.

The current amplitude comparator 434 in FIG. 4 is an example of acomparator that compares amplitudes of a plurality of analog currentdetection signals to one another and produces the selection signal independence on which one of the analog current detection signal has agreatest amplitude. As explained above, in an alternative embodiment,the comparator can be a phase comparator that produces the selectionsignal in dependence on which one of the two or more analog currentdetection signals has a lowest phase difference relative to a transmitsignal or some other reference signal.

Referring to FIGS. 3 and 4, in accordance with an embodiment the latch436 of the comparator 324 can be implemented, e.g., using a set-reset(SR) flip-flop, or a D flip-flop, but is not limited thereto. If thelatch 426 is implemented using an SR flip-flop, the SR flip-flop can bereset using the transmit (TX) signal, and can be set using a delayedversion of the TX signal so that it is set at a predetermined timeinterval after the TX signal causes the light source 104 to emit a pulseor burst of light. This can be achieved, e.g., by providing the TXsignal to a reset (R) input of the SR flip-flop and by using a delaycircuit to provide a delayed version of the TX signal to a set (S) inputof the SR flip-flop. In accordance with an embodiment, at a predeterminetime interval after the SR flip-flop is set, the ADC 120 can betriggered to perform a conversion. This can be achieved, e.g., by usinga further delay circuit to provide a further delayed version of the TXsignal to a conversion triggering input of the ADC 120. Instead of usingthe aforementioned delay circuits to produce the set and reset signals,a controller (e.g., 108 in FIG. 3 or 608 in FIG. 6 discussed below) cangenerate the set and reset signals and provide them directly to thelatch 436. More generally, a controller (e.g., 108 or 608) can generatethe timing signals used to control the comparator 324 and the ADC 120.FIG. 7 illustrates an exemplary timing diagram for exemplary signalsthat can be used to control the light source 104, the comparator 324 andthe ADC 120.

Embodiments of the present invention are also directed to methodsdescribed below with reference to FIG. 5, wherein such methods can,e.g., be performed using the embodiments described above with referenceto FIG. 3, and potentially also using the embodiment described withreference to FIG. 4 and FIG. 6. More specifically, certain embodimentsrelate to methods for producing a digital output indicative of which PD,of a plurality of PDs, has a closest object to the PD within the FOV ofthe PD. Details of such a method will now be described with reference tothe high level flow diagram of FIG. 5

Referring to FIG. 5, step 502 involves selectively driving one or morelight sources to emit light. Step 504 involves producing, at each of aplurality of photodetectors (PDs) that each have a respective field ofview (FOV), a respective analog current detection signal indicative oflight emitted by one more light sources that reflected of an objectwithin the FOV of the PD and is incident on and detected by the PD. Step506 involves comparing the plurality of analog current detection signalsproduced by the plurality of PDs to thereby determine which PD has aclosest object to the PD within the FOV of the PD. In accordance withcertain embodiments, step 506 is performed by comparing amplitudes ofthe analog current detection signals produced by the plurality of PDs todetermine which analog current detection signal has a greatestamplitude. Alternatively, step 506 can be performed by determining whichone of the analog current detection signals has a lowest phasedifference relative to a transmit signal that is used to selectivelydrive the light source(s) at step 502, or relative to some otherreference signal. Additional details of such methods can be appreciatedfrom the above descriptions of FIGS. 1-4.

Still referring to FIG. 5, step 508 involves producing a digital outputcorresponding to the analog current detection signal produced by the PDthat has a closest object within its FOV. If only one of the PDs have anobject within its FOV, then the digital output produced at step 508 willbe indicate which PD has the object within its FOV. If more than one ofthe PDs has an object within its FOV, then the digital output producedat step 508 will indicate which of the PDs (that has an object withinits FOV) has the closest object to the PD. Still referring to FIG. 5,step 510 involves selecting one of a plurality of different possibleresponses or actions in dependence on the digital output produced at508. The selecting one of a plurality of different possible responses oractions at step 510 can also be in dependence on the results of thecomparing at step 506, so that the selecting of a response or action isalso based on which FOV included an object or closet object.Additionally, or alternatively, step 510 can involve selectivelyenabling or disabling a subsystem in dependence on the digital outputproduced at step 508. The selectively enabling or disabling a subsystemat step 510 can also be in dependence on the results of the comparing atstep 506, so that the selectively enabling or disabling is also based onwhich FOV included an object or closet object.

For an example, the above described method can be used by a controllerof an autonomous robot to detect when an object is in the path of therobot, so that the robot can be controlled to move around the object,which in this example can also be referred to as an obstacle. The robotmay have two or more PDs that are spaced about a perimeter of the robot,with each of the PDs having its own field of view (FOV). The PDs can beused, in combination with one or more light sources, to determine whenan object is within one of the FOVs. Or, if more than one of the PDs hasan object within its FOV, then the method can be used to determine whichof the PDs (that has an object within its FOV) has the closest object tothe PD. Such information can be used to assist in controlling the robotto navigate around object(s) without colliding with the object(s). For amore specific example, while a robot is traveling in a particulardirection, the method can be used to determine that there is an objectwithin the path that the robot is traveling, but that there is no objectto the left of the robot, which would enable the robot to be controlledto turn left to avoid colliding with the object that was in its path.For another example, the above method can be used by a system or devicethat includes keys or buttons, each of which has its own PD, todetermine which key or button is being selected by a user, and anappropriate response can be activated based on which key or button isdetermined to have been selected. These are just a few examples, whichare not intended to be all encompassing.

FIG. 6 illustrates an exemplary system 602 according to an embodiment ofthe present invention. The system 602 is shown as including a pluralityof light sources 104 ₁, 104 ₂ . . . 104 _(n), but can alternativelyinclude a single light source 104. The system 602 is also shown asincluding a plurality of drivers 106 ₁, 106 ₂ . . . 106 _(n), but canalternatively include a single driver 106. The system is also shown asincluding a plurality photodetectors (PDs) 114 ₁, 114 ₂ . . . 114 _(n)each having a respective field of view (FOV) and each producing arespective analog current detection signal indicative of light incidenton and detected by the PD 114. The plurality of PDs 104 can be as few astwo PDs. A winner-take-all (WTA) circuit 326 receives the plurality ofanalog current detection signals produced by the plurality of PDs 114and outputs the one of the analog current detection signals thatcorresponds to the PD having a closest object within its FOV. This meansthat if there is an object within only one of the FOVs, then the analogcurrent detection signal output by the WTA circuit 326 corresponds tothe only PD having the object within its FOV; and if there is an objectwithin more than one of the FOVs, then the analog current detectionsignal output by the WTA circuit 326 corresponds to the PD having theclosest object within its FOV. One object can be within more than oneFOV and/or different objects can be within different FOVs.

Still referring to FIG. 6, the system 602 is also shown as including atransimpedance amplifier (TIA) 116 that converts the one of the analogcurrent detection signals, output by the WTA circuit 326, to an analogvoltage detection signal. An amplifier 118, which in this example is aprogrammable gain amplifier (PGA), amplifies the analog voltagedetection signal to produce an amplified analog voltage detectionsignal. An analog-to-digital converter (ADC) 120 converts the amplifiedanalog voltage detection signal to a digital detection signal. Thedigital detection signal is provided to a controller 608. The controlleris also shown as receiving the selection signal produced by thecomparator 324, or more generally, by the WTA circuit 326. As explainedabove, the selection signal indicates which PD 114 has the closestobject within its FOV.

In the embodiment shown in FIG. 6, the WTA circuit 326 includes acomparator 324 that compares the plurality of analog current detectionsignals produced by the plurality of PDs 104 and produces a selectionsignal in dependence thereon. The WTA circuit 326 also includes amultiplexor (MUX) 322 that receives the plurality of analog currentdetection signals produced by the plurality of PDs 104 and outputs oneof the analog current detection signals in dependence on the selectionsignal produced by the comparator 324. As was discussed above, thecomparator 324 can compare amplitudes of the plurality of analog currentdetection signals to one another and produce the selection signal independence on which one of the analog current detection signal has agreatest amplitude. Alternatively, as was also explained above, thecomparator 324 can produce the selection signal in dependence on whichone of the analog current detection signals has a lowest phasedifference relative to a transmit (TX) signal that is used to controlthe selective driving of the light source(s) 104, or relative to someother reference signal. It is also possible that the comparator 324compares both amplitudes and phase differences to produce its selectionsignals based on both amplitudes and phase differences.

The system is also shown as including a subsystem 610. The subsystem 610can be selectively enabled or disabled by the controller 608 independence on the digital detection signal output by the ADC 120.Additionally, or alternatively, the controller 608 can selects one of aplurality of different possible responses or actions in dependence onthe digital detection signal output by the ADC 120. As mentioned above,the controller 608 can also receive the selection signal produced by thecomparator 324, or more generally by the WTA circuit 326, so that thecontroller 608 knows which PD 114 and FOV is associated with the digitaldetection signal output by the ADC 120. Based on such information thecontroller 608 can, for example, determine how to maneuver a robot,determine what warning message to issue, determine what light to turnon, or the like.

In accordance with an embodiment, if the digital signal output by theADC 120 is below a specified threshold, it can be assumed that the PDs114 are just picking up optical noise, and that there is not really anobject within the FOV of any of the PDs 114. The controller 608 can, forexample, compare the output of the ADC 120 to a threshold to determinewhether or not the digital output of the ADC 120 is actually indicativeof an object being within one of the FOVs. Other implementations arealso possible, as would be understood by one or ordinary skill in theart.

Embodiments described herein can be implemented as an applicationspecific integrated circuit (ASIC). Alternatively, embodiments describedherein can be implemented using discrete components. Other variationsare also possible and within the scope of an embodiment. A controller,implemented as a processor, microcontroller unit (MCU) or state machine,but not limited thereto, can be used to control the optical proximitydetectors described herein.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample, and not limitation. It will be apparent to persons skilled inthe relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.

The breadth and scope of the present invention should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

What is claimed is:
 1. An optical proximity detector, comprising: aplurality photodetectors (PDs) each having a respective field of view(FOV) and each producing a respective analog current detection signalindicative of light incident on and detected by the PD; a comparatorthat compares the plurality of analog current detection signals producedby the plurality of PDs and produces a selection signal in dependencethereon; a multiplexor (MUX) that receives the plurality of analogcurrent detection signals produced by the plurality of PDs and outputsone of the analog current detection signals in dependence on theselection signal produced by the comparator; and circuitry that producesa digital detection signal corresponding to the one of the analogcurrent detection signals output by the MUX.
 2. The optical proximitydetector of claim 1, wherein: when only one of the plurality of PDs hasan object within its FOV, the digital detection signal output by thecircuitry corresponds to the PD having the object within its FOV; andwhen more than one of the plurality of PDs has an object within its FOV,the digital detection signal output by the circuitry corresponds to thePD have a closest object relative to the PD within its FOV.
 3. Theoptical proximity detector of claim 1, wherein the circuitry thatproduces a digital detection signal corresponding to the one of theanalog current detection signals output by the MUX comprises: atransimpedance amplifier (TIA) that converts the one of the analogcurrent detection signals, output by the MUX, to an analog voltagedetection signal; an amplifier that amplifies the analog voltagedetection signal to produce an amplified analog voltage detectionsignal; and an analog-to-digital converter (ADC) that converts theamplified analog voltage detection signal to the digital detectionsignal corresponding to the one of the analog current detection signalsoutput by the MUX.
 4. The optical proximity detector of claim 1, whereinthe comparator compares amplitudes of the plurality of analog currentdetection signals to one another and produces the selection signal independence on which one of the analog current detection signal has agreatest amplitude.
 5. The optical proximity detector of claim 1,wherein the comparator produces the selection signal in dependence onwhich one of the analog current detection signals has a lowest phasedifference relative to a reference signal.
 6. The optical proximitydetector of claim 1, further comprising: one or more light sources; anda driver that selectively drives the one or more light sources, to emitlight, in dependence on a transmit signal; wherein each PD, of theplurality of PDs, detects light emitted by at least one of the one ormore light sources that has reflected off an object, if any, within theFOV of the PD and produces the analog current detection signal independence thereon.
 7. The optical proximity detector of claim 6,further comprising a controller that produces a transmit signal that isprovided to the driver and the comparator.
 8. A method, comprising: (a)producing, at each of a plurality of photodetectors (PDs) that each havea respective field of view (FOV), a respective analog current detectionsignal indicative of light emitted by one more light sources thatreflected of an object, if any, within the FOV of the PD and is incidenton and detected by the PD; (b) comparing the plurality of analog currentdetection signals produced by the plurality of PDs to thereby determinewhich PD has a closest object to the PD within the FOV of the PD; and(c) producing a digital output corresponding to the analog currentdetection signal produced by the PD that has a closest object to the PDwithin the FOV of the PD.
 9. The method of claim 8, wherein: step (b)includes comparing amplitudes of the analog current detection signalsproduced by the plurality of PDs to determine which analog currentdetection signal has a greatest amplitude.
 10. The method of claim 8,wherein: steps (b) includes determining which one of the analog currentdetection signals has a lowest phase difference relative to a referencesignal.
 11. The method of claim 8, further comprising, prior to step(a), selectively driving one or more light sources to emit light. 12.The method of claim 8, further comprising, after step (c), selecting oneof a plurality of different possible responses or actions in dependenceon the digital output produced at step (c).
 13. The method of claim 12,wherein the selecting one of a plurality of different possible responsesor actions is also in dependence on the results of the comparing at step(b).
 14. The method of claim 8, further comprising, after step (c),selectively enabling or disabling a subsystem in dependence on thedigital output produced at step (c).
 15. A system, comprising: one ormore light sources that are selectively driven to emit light; aplurality photodetectors (PDs) each having a respective field of view(FOV) and each producing a respective analog current detection signalindicative of light, emitted by at least one of the one or more lightsources, that has reflected off an object, if any, with the FOV of thePD and is incident on and detected by the PD; a winner-take-all (WTA)circuit that receives the plurality of analog current detection signalsproduced by the plurality of PDs and outputs one of the analog currentdetection signals that corresponds to the PD having a closest objectwithin its FOV; and circuitry that produces a digital detection signalcorresponding to the one of the analog current detection signals outputby the WTA circuit.
 16. The system of claim 15, wherein the WTA circuitcomprises: a comparator that compares the plurality of analog currentdetection signals produced by the plurality of PDs and produces aselection signal in dependence thereon; and a multiplexor (MUX) thatreceives the plurality of analog current detection signals produced bythe plurality of PDs and outputs one of the analog current detectionsignals in dependence on the selection signal produced by thecomparator; wherein the one of the analog current detection signalsoutput by the MUX is the one of the analog current detection signalsoutput by the WTA circuit.
 17. The system of claim 16, wherein thecomparator compares amplitudes of the plurality of analog currentdetection signals to one another and produces the selection signal independence on which one of the analog current detection signal has agreatest amplitude.
 18. The system of claim 16, wherein the comparatorproduces the selection signal in dependence on which one of the analogcurrent detection signals has a lowest phase difference relative to areference signal.
 19. The system of claim 16, further comprising: acontroller that selectively enables or disables a subsystem, or selectsone of a plurality of different possible responses or actions, independence on the digital detection signal and the selection signalproduced by the comparator.
 20. The system of claim 14, furthercomprising: a controller that selectively enables or disables asubsystem, or selects one of a plurality of different possible responsesor actions, in dependence on the digital detection signal.